feat(electron): 添加Electron桌面应用支持

- 新增Electron主进程、预加载脚本和构建配置
- 修改前端配置以支持Electron打包
- 更新项目文档和依赖
- 重构API调用使用统一axios实例

app/package.json

@@ -0,0 +1,13 @@
+{
+  "name": "bidding-app",
+  "version": "0.0.1",
+  "description": "投标应用Electron版本",
+  "main": "main.js",
+  "scripts": {
+    "start": "electron .",
+    "build": "electron-builder"
+  },
+  "keywords": ["electron", "bidding", "app"],
+  "author": "",
+  "license": "UNLICENSED"
+}